Lubricating oil composition containing heterocyclic polyamine salts of partial ester of phosphorodithioic acid as antiwear agent



LUBRICATING OIL COMPOSITION CONTAINING HETEROCYCLIC POLYAMINE SALTS OFPAR= TIAL ESTER F PHOSPHORODITHIOIC ACID AS ANTIWEAR AGENT Allen F.Millikan, Crystal Lake, and Giiford W. Crosby, River Forest, lll.,assignors to The Pure Oil Company, Chicago, 111., a corporation of OhioNo Drawing. Filed Dec. 31, 1956, Ser. No. 631,516

Claims. (Cl. 252-3237) I This invention relates to lubricants and moreparticularly to lubricants containing small amounts of heterocyclicpolyamine salts of partially esterified phosphorodithioic acids added toimprove the load-carrying, antiwear and oxidation-resistancecharacteristics of the mineral oil.

The addition of salts of alkyl dithiophosphoric acids such as the zincsalts, to mineral oils in order to improve the wear-resistancecharacteristics of such oils is well known. We have discovered that if apartially esterified phosphorodithioic acid is combined with aheterocyclic polyamine to form a salt, the resulting salt hassubstantially better anti-wear characteristics than other types of amineor metal salts.

One of the objects of our invention is to provide a lubricating oilhaving improved anti-wear characteristics. Another object of ourinvention is to provide a lubricant having improved load-carrying,anti-wear and oxidationresistance characteristics. Other objects of theinvention will become manifest from the following disclosure.

In accordance with our invention there is added to mineral lubricatingoil a small amount of a salt of a heterocyclic polyamine containing atleast one atom of nitrogen in the tri-coordinated state and partiallyesterified phosphorodithioic acid. The heterocyclic polyamines which maybe used in forming the salt useful in our invention include cyclo di-,triand tetramines. As examples of heterocyclic polyamines useful informing the partially esterified phosphorodithioate salts aretetrarnines such as hexamethylenetetramine; triamines such as thetrialkylcyclotrirnethylenetriamines.

CH2 which may be prepared by reacting primary aliphatic amines andformaldehyde; piperazine and alkyl-substituted piperazines; andalkylisomelamines The partial esters of phosphorodithioic acids withwhich the heterocyclic polyamines are combined to form 2,973,323Patented Feb. 28, 1961 tain 4 to 20 carbon atoms and preferably thosepartial esters which contain two hydrocarbon groups. These groups maycontain other substituents, such as oxygen, sulfur and nitrogen in theform of hydroxyl, thiol or amino radicals. As specific examples of saltsuseful in our invention the following are given:

(1) Piperazine salt of 0,0-di-2-ethylhexyl phosphorodithioic acid (2)N,N-dibutylpiperazine salt of 0,0-di-(octylphenyl) phosphorodithioicacid (3) Eethylisomelamine salt of 0,0-didecyl phosphorodithioic acid(4) Hexamethylenetetramine salt of 0,0-didodecyl phosphorodithioic acid(5) Piperazine salt of S,S-didodecyl phosphorodithioic acid (6)Hexamethylenetetramine salt of 0,0-di-2-ethylbutyl phosphorodithioicacid (7) N,N-dioctylpiperazine salt of 0,0-diphenyl phosphorodithioicacid (8) Hexamethylenetetramine salt of 0,0-di(phenylpropyl)phosphorodithioic acid (9) N,N,N-trimethyltrirnethylenetriamine salt of0,0- di-2-ethylhexyl phosphorodithioic acid.

The heterocyclic polyamine salts of partial esters of dithiophosphoricacids may be added to the lubricating oil in amounts of approximately0.05 to 0.5% by weight phosphorus equivalent. We have found that if theamount of salt is equal to about the equivalent of 0.1 weight percent ofphosphorus, a very significant improvement in anti-wear characteristicsof the oil is obtained.

The above-described compounds are disclosed and claimedv as novelcompounds in our copending application Serial No. 655,011, filed April25, 1957, now Patent 2,894,951.

The polyamine salts of our invention may be added to lubricating oilstogether with other well-known additives, such as detergents, pour pointdepressants and viscosity index improvers.

The salts useful in our invention may be prepared by reacting thedesired heterocyclic polyamine with the desired partially esterifiedphosphorodithioate. Another method of preparing heterocyclic aminesfalling within the scope of our invention is by reacting a partiallyesterified dithiophosphoric acid with an aldehyde and excess ammonia.The following are specific examples which are illustrative of the mannerin which the compounds of our invention may be prepared.

EXAMPLE I To 195 grams of 2-ethylhexyl alcohol, 195 grams of toluene and195 grams of solvent-refined neutral oil having an SUS viscosity of 85at 100 F. there was added 83.5 grams of phosphorus pentasuliide-so thatthe mixture contained 1.5 mols of the alcohol to 0.38 mol of phosphoruspentasulfide. The mixture was stirred for four hours on the steam bathand the resulting acid solution then filtered and treated with 133 grams(0.94

mol) of hexamethylenetetramine at room temperature. After the mixturewas allowed to react for 16 hours it was diluted with hexane and excesshexamethylenetetramine separated by filtration. A crystallized productsalts include alkyl, aryl, aralkyl and alkaryl dithiophosseparated fromthe filtrate on chilling to a temperature of 30 F. attained a yield ofUpon recrystallizing the product from hexane, a white solid was obtainedhaving a melting point of 69-70 C. and analyzing nitrogen 10.5%,phosphorus 6.1%, sulfur 12.8%. These values are close to the calculatedvalues of 11.3% nitro- 3 gen, 6.3% phosphorus and 13% sulfur forhexamethylenetetrammonium di-2-ethylhexyldithiophosphate.

EXAMPLE 'II Di-Z-ethylhexyl dithiophosphoric acid prepared as in theprevious example was reacted with one eq ivalent of paraformaldehyde andan excess of anhydrous ammonia at room temperature for a period of onehour. The solvent (toluene) and excess ammonia was then removed byvacuum stripping in the presence of nitrogen and the liquid product wasclarified by filtration through celite. Analysis of the resulting liquidproduct gave a ratio of nitrogen to phosphorus of 1.6, which wouldcorrespond to a mixture of hexamethylenetetramine orcyclotrimethylenetriamine salts of the partially esterifiedthiophosphoric acid with ammonium salts of the same acid.

Table I Four-Ball Transition Point to High Wear Rate Load in Kg.

Anti-wear Additive Mireral. Oil-94.1 pts. by

W Basic Ba pet. sulionate 5.3 pts. by Wt. Suliurized terpene 65 pts. byW Mineral Oi194.1 pts. by

Basic Ba pet. Sultanate- 5.3 pts. by Wt.

Sulfurized terpene0.65

M by wt. Minteral Oil-94.1 pts. by

W Basic Ba pet. su1tonate 5.3 pts. by wt. Sulfurized terpene0.65

pts. by w Mirieral Oil-94.1 pts. by

w 4 Basic Ba pct. sulfonate- 5.3 pts. by wt.

Sulfurized terpene0.0 pts. by wt.

1--- None 60 Ammonium di-2-ethyl hexyl dithiophos- 90 phate. 1

Complex salt of Example 100 Salt of Example 1 Q 130 1 Contained incomposition (1) in amount of equivalent to 0.1% by weight of phosphorus.

In order to demonstrate the wear-resisting characteristics of compoundswithin the scope of our invention, solvent-refined neutral oil having anSUS viscosity of 170 at 100 F. and containing basic barium petroleumsulfohate as a detergent and sulfurized terpenes as corrosion inhibitorwas tested in accordance with the Four-Ball Test briefly described onpages 13 and 14 of The Performance of Lubricating Oils, by Zuidema,published in 1952 by Reinhold Publishing Corporation, New York. Thesulfurized terpene corrosion inhibitor is a product of 29.4 wt. percentsulfur which is available on the market. The basic barium sulfonate wasprepared by sulfonating a mineral lubricating oil fraction with sulfurtrioxide at a temperature of below 120 F. and neutralizing the resultingsulfonic acids with an excess of barium hydroxide octahydrate. This oilwas tested with and without antiwear additives for purposes ofcomparison. The results are given in Table I.

From an examination of Table I it is apparent that the oil to which theinhibitor prepared in accordance with Example I was added improved theload at which transition to high Wear took place by over 100%. Thecomplex salt made in accordance with Example II increased the load atwhich transition to high Wear occurred by almost Whereas the ammoniumdi-Z-ethylhexyl dithiophosphate only improved the transition point by50%.

In order to further demonstrate the superiority of salts falling Withinthe scope of our invention over other types of amine or metal salts,Mid-Continent refined neutral oil having an SUS viscosity of 170 at 100F., containing phenol extract resulting from the solvent-refining of theoil, barium alkyl phenol sulfide-calcium sulfonate detergent availableon the market, and mixed alcohols-methacrylate polymer pour pointdepressant and viscosity index improver, also available as a commercialproduct, was tested with and without various dithiophosphoric acid saltsin which the amount of salt added was equivalent to 0.1 weight percentof phosphorus. The results of the tests are given in Table II. Furtheridentification of the above commercial additives is as follows. Bariumand calcium contents of the detergent additive were 8.1 and 0.6 wt.percent respectively. The average molecular weight of the methacrylatepolymer was in the 10,000 to 20,000 range.

Table II Transition Point to High Wear Rate Load in Kg.

Anti-wear Additive Mineral oil84.2 parts by vol Phenol extract4.5 partsby vol Ba alkylphenolsulfide Ca sulfonat Mineral oil-84.2 parts byVOL--. Phenol extract-4.5 parts by vol Baalkylphenolsulfide Ca sulfonatMineral oil-84.2 parts by vol Phenol extract-4.5 parts by vol. Baalkylphenolsulfide 0a sulfonat Mineral oil84.2 parts by vol Phenolext-raet4.5 parts by vol Ba alkylphenolsulfide Ca sulfonate Mineraloil-84.2 parts by vol Phenol extract-4.5 parts by vol Baalkylphenolsulfide Ga sulfonate- Methacrylate polymer-6.3 parts by vblMethacrylate polymer-6.3 parts by vol Mineral nib-84.2 parts by volPhenol extract4.5 parts by vol Ba alkylphenolsulf de .Ca sulf0nate -5.0parts by v0 Methacrylate polymer-6.3 parts by vol parts by v0 parts byvo Methaerylate polymer-6.3 parts by vol parts by v0 e parts by volMethacrylate polymer6.3 parts by vol parts by vol Methacrylatcpolymer6.3 parts by vol .0 parts by vol Methacryiate polymer-6.3 partsby vol None 50 +Salt'of Example I +Aniline salt of 'di-2-ethylhexylphosphorodithioic acid.

+Tripheny1guanidine salt of di-2-ethylhexyl s0 phosphorodlthioic acid.

+Phenylguanidine salt of di-2-ethylhexyl phosphorodithioic acid.

+Piperidine salt of di2-ethylhexyl phospho- 80 rodithioic acid.

lllltllllllll +Zinc salt of di-2-ethy1hexy1 phosphorodi- 100 thioicacid.

From an inspection of Table II it will be seen that while amine saltsand zinc salts in general increased the load point at which transitionto high rate occurred, the hexamethylenetetramine salt (the only salt inTable II falling within the scope of the present invention) is superiorto any of the other compounds tested and raised the loadcarrying abilityof the oil by 140%.

In the foregoing examples the detergent, pour depressant and viscosityimprover are not necessary ingredients of the oil insofar as the presentinvention is concerned but are added to the oil merely to 'give abalanced oil corresponding to one which would be used in actualcommercial practice.

It will be seen, therefore, that we have found a select group of aminesalts which have unusual ability in improving the anti-wearcharacteristics of mineral lubricating oils.

We claim as our invention:

1. A lubricant composition comprising a major portion of a minerallubricating oil and a minor portion, sufiicient to enhance substantiallythe load-'carrying'properties of the oil, of at least one heterocyclicpolyamine salt of a phosphorodithiotic acid ester of the formula where Ris a C -C radical selected from the group consisting of alkyl, phenyl,alkylphenyl, and phenylakyl radicals, and where the hetcrocyclicpolyamine is selected from the group consisting ofhexamethylenetetramine, trilower alkyl cyclotrimethylene triamines,piperazine, lower alkyl-substituted piperazines, and lower alkylisomelamines.

2. A lubricating oil in accordance with claim 1 in which the polyamineis a trialkylcyclotrimethylenetriamine.

3. A lubricating oil in accordance with claim 1 in which the polyamineis a piperazine.

4. A lubricating oil in accordance with claim 1 in which the polyamineis an alkylisomelamine.

5. A lubricating oil in accordance with claim 1 containing an amount ofsaid salt equivalent to about 0.05 to 0.05% by weight of phosphorus.

6. A lubricating oil in accordance with claim 1 in which the salt is ahexamethylenetetramine salt of a dialkyl phosphorodithioic acid.

7. A lubricating oil in accordance with claim 6 in which the salt ishexamethylenetetrammonium di-Z-ethylhexyl phosphorodithioate.

8. A lubricating oil in accordance with claim 7 containing an amount ofsaid salt equivalent to about 0.05 to 0.5% by weight of phosphorus.

9. A lubricating oil composition in accordance with claim 1 whichcontains a small amount of a detergent and a corrosion inhibitor.

10. A lubricating oil composition in accordance with claim 9 in whichthe detergent is a basic barium petroleum sulfonate and the corrosioninhibitor is a sulfurized terpene.

References Cited in the file of this patent UNITED STATES PATENTS2,167,867 Benning Aug. 1, 1939 2,316,587 Irigai Apr. 13, 1943 2,447,288Smith et a1 Apr. 17, 1948 2,640,209 Blair et a1. May 26, 1953 2,676,150Loughran et al. Apr. 20, 1954 2,679,481 Norris et al. May 25, 19542,683,691 Thorpe et al. July 13, 1954 2,712,526 McDermott July 5, 19552,767,165 Smith et al. Oct. 16, 1956 2,773,861 Musselman Dec. 11, 19562,773,862 Musselman Dec. 11, 1956 2,798,045 Buck et al. July 2, 1957UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No.,2,973,323 February 28, 1961 Allen F. Millikan et a1.

It is hereby oertified'that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 6 line 5 for "0,05%" read 05 (SEAL) Attest:

ERNEST W. SWIDER Attesting Officer DAVID L. LADD Commissioner of Patents

1. A LUBRICANT COMPOSITION COMPRISING A MAJOR PORTION OF A MINERALLUBRICATING OIL AND A MINOR PORTION, SUFFICIENT TO ENHANCE SUBSTANTIALLYTHE LOAD-CARRYING PROPERTIES OF THE OIL, OF AT LEAST ONE HETEROCYCLICPOLYAMINE SALT OF A PHOSPHORODITHIOTIC ACID ESTER OF THE FORMULA